The basic procedure for commercially producing mushrooms involves an initial step of impregnating a suitably prepared compost with mushroom mycelia. This step is referred to as "spawning", and is generally done in a plurality of individual beds or trays to facilitate handling and to economize space. The compost provides the nutrients, e.g., amino acids, essential for mycelium growth. The compost is often prepared from a mixture of horse manure and straw suitably treated, according to well known procedures, to yield a final composition promotive of mushroom growth. The mycelium-impregnated compost is then allowed to develop under carefully controlled conditions of temperature and moisture, until the hyphae of the mycelium have permeated the compost. This process usually takes anywhere from two to three weeks. At this time, the mycelia-permeated compost is covered with a thin layer of soil or sand; peat is often used. This step is referred to as "casing", and the presence to this top layer causes the mushrooms to "flower", i.e., to form the fleshy fruiting body harvested as the product. It genrally takes about three weeks after the beds are cased for the first mushrooms to appear. After harvesting the first crop of mushrooms, the bed goes through another growth cycle in which additional mushroom fruits are produced. These growth cycles are referred to as "breaks", and a commercial compost bed generally undergoes three to five breaks before the compost becomes significantly depleted in essential nutrients. The compost is then discarded and the procedure is initiated anew.
The prior art has shown that enhanced mushroom yields can be obtained by adding supplementary nutrients to the compost bed. For example, in Hughes et al. U.S. Pat. No. 3,560,190 a dry formulation based on a combination of cottonseed meal and cottonseed oil is disclosed as a suitable supplement. It is also known to use cracked soybeans as a supplement, i.e., soybeans that have been broken into smaller pieces of about 1/6 to 1/10 the size of the whole bean. These materials have been added to the compost bed both at the time of spawning and casing.
Nutrient supplementation, however, is susceptible to some undesirable side effects. One problem that has been encountered is excessive bed heating, apparently caused by the ready availability of the nutrient source to the highly active microbial mushroom culture. Temperature excursions above 35.degree. C. (95.degree. F.), sufficient to significantly deplete, if not completely destroy the mushroom mycelia have been observed. Another problem is encountered when adding the supplement to the compost at the time of spawning. In many cases other micro-organisms, primarily molds, pre-existing in the compost, introduced with the supplement, or introduced via airborne contamination, compete with the mushroom mycelium for the added nutrients. This reduces the availability of the supplement for its intended purpose and often hinders the development of the mushroom mycelium.
Recognizing these problems, Carroll et al. U.S. Pat. No. 3,942,969 provides a supplement suitable for addition to the compost at the time of spawning, in which the release of the nutrient is delayed. This supplement comprises a denatured protein source, including proteins derived from cottonseed, soybean and peanuts. As disclosed, the denaturing can be accomplished by heating or by treatment with alkalies, acids or formaldehyde. Unfortunately, the potential gains in mushroom yields, are disadvantageously offset by the economic penalty associated with the denaturation treatment.
It is an object of the invention to provide a mushroom supplement for increasing the yield of mushrooms in commercial mushroom production.
It is another object of this invention to provide a mushroom supplement having a delayed release of nutrients for stimulating mycelium growth.
It is a further object of this invention to provide a mushroom supplement that can be added to the compost either at spawning or up to casing.
It is yet another object of this invention to provide a mushroom supplement that is more economical to produce than the denatured protein of Carroll et al.